1. Scope of Invention
This invention relates generally to plumb bobs, and more particularly to a self-leveling laser beam type plumb apparatus.
2. Prior Art
In building construction and ceiling installation and in other areas within building and homes, many times it becomes necessary to locate a spot or a line, or a series of either, onto an overhead structure or ceiling of the building. To accomplish this, the marks or lines are first typically laid out on the floor or horizontal working surface and then, using a conventional gravity plumb bob, two men are required to effect the transfer, one person holding the upper end of the string of the plumb bob against the overhead surface while the other insures that the lower pointed end of the plumb bob itself is positioned by gravity over the corresponding marks and lines on the floor.
A number of devices have been patented which facilitate this procedure. Abrams, in U.S. Pat. No. 3,505,739 teaches an apparatus for transferring floor to ceiling markings. A gimbal arrangement in conjunction with an incandescent bulb projected "x" directly above the lower pointed end of its plumb bob effects this procedure. However, Abrams projects an ever-increasingly large and obscure "x" as a shadow and also includes more complex gimbal arrangements which may be difficult to maintain in precise working order.
In U.S. Pat. No. 5,537,205, Costa also teaches a self-leveling laser plumb assembly which utilizes a gimbal arrangement for vertically aligning by gravity a housing which holds a laser beam unit mounted axially within the housing. The delicacy of the gimbal arrangement and the accuracy with which the laser unit projects a true axial beam in precision alignment with the longitudinal axis of the plumb bob is questionable.
Another portable laser plumb line indicator is taught by McManus in U.S. Pat. No. 4,448,528. This disclosure teaches a somewhat more complex and expensive apparatus which claims to direct a truly accurate laser beam both downwardly to the mark on the floor and upwardly to the point on the ceiling or overhead structure. This apparatus is quite complex and expensive to manufacture and appears only useful for more sophisticated and complex projects.
Applicant is also aware of the following additional U.S. patents which are somewhat more remotely related to the present invention:
Rooney U.S. Pat. No. 5,481,809 PA1 Chase U.S. Pat. No. 5,572,797 PA1 Trice U.S. Pat. No. 3,591,926 PA1 DiMaggio U.S. Pat. No. 5,012,585 PA1 Studebaker U.S. Pat. No. 3,588,249 PA1 Ohneda U.S. Pat. No. 3,911,588 PA1 Butler U.S. Pat. No. 5,680,208
The present invention provides a very economical to manufacture and easily useable and dismantleable laser plumb bob which, by utilization of the herebelow described laser beam alignment fixture, provides an extremely accurate, yet economical tool for the transfer of floor or work surface mounting markings up to a ceiling or other overhead structure. The laser beam alignment fixture and procedure taught by this application have been shown to be of extreme importance with respect to the ultimate accuracy of the laser beam projections of floor markings due to the fact that a part of the economy of the present invention derives from the utilization of low cost currently manufactured miniature laser beam units which do not project a laser beam therefrom which is in precise axial alignment with the physical longitudinal structure thereof.